Launching the game after reinstalling Windows (Assassin's Creed: Unity)

Good morning, dear)
The problem is this:
Friend, reinstalled Win, from win7x64 to win7x64 due to the consequences of the virus, he did not delete the game, he left it on the second hard partition. After reinstalling the system, drivers and other important libraries for games, etc., he checked all the games and they all successfully started on a clean Windows and picked up the saves. But there is no Unity, when you try to run it, it opens Steam on the game page, without Steam, the game gives an error and suggests looking for a solution on the net. In short, is it possible to somehow restore the missing files, which apparently were registered in system folders such as program data local, etc.? He really doesn’t want to download the game again and reinstall it. Maybe someone knows a way, can someone share these files !?
ps - a pirate game, whose repack is xs, but it probably doesn't matter.
Thank you.